Battery chargers are meant to do that. They'll charge at high amperage until it's about 80% full, then go to about 3 or 4% and maintain that. It won't ever truly be 100%.
Newer chargers anyway. Say maybe last 15 years or so. I think.
Here's what I've learned with my trailer. Use a charger if it's dead and you need to use today. Otherwise, use a tender. Totally different from a charger.
I use the actual Battery Tender brand. It'll take three completely dead deep cycle batteries and fully charge them in about three days. Then maintain a true 100% charge indefinitely. And it's a true charge.
The average battery charger will only give you about 85-87% charge and can set a memory in the battery. Tenders don't do this. But the upside to a charger is how quick you'll get that charge. So I keep both handy
